Thanks, so it was just one of the updates of the 12C that used the Sunplus then. So, were they emulating the original architecture with the Sunplus like they did on the ARM versions?

I saw on this forum and one other place as I recall that the HP-35S also used the Sunplus.

I was watching an interview with Prof. Kahan yesterday, who helped HP with the software used on some of their calculators and he briefly mentioned something about a 6502. It did not register with me until much later. I was just searching the here specifically and the intertubes in general and it ...

TASM + VS Code, just did a video about it: https://youtu.be/kamDP5FA6Bg

Curious Marc did a series recently fixing six different HP 98035 clock modules. In one of them he found that the new inverter chip he installed for the clock generation did not work and traced it down to the different analog specifications/characteristics of different chips. He wound up changing the ...

This is Part#2 where we take an in depth look at how the ‘Cruncher’ software, written in C#, works to take the output from Audacity, and further process it to generate the data format required to play back via the C64 SID chip. We then do a deep dive into the DIGI player code itself that runs on C64 ...

Earlier this year I had asked a couple questions on the forum here about a project I was working on to play 'DIGIs', digital speech samples, on a C64. One question was about methods to toggle a bit flag and the other was about choosing which ISR to use at run-time. Lot's of great suggestions were ...

I was just referencing the 6502 opcodes page concerning the BIT instruction and noticed that is says "S and V flags" rather then "N and V flags". I'm not sure who maintains this page do I'm posting this here.

BIT (test BITs)
Affects Flags: N V Z

MODE SYNTAX HEX LEN TIM
Zero Page BIT $44 $24 2 3 ...

I'm not going mad!!

When working on the problem of cleaning exiting back to BASIC after the player stopped it seemed that none of the changes I was making were having an effect. I finally set $0400 to display an A character and when that did not show up I new VICE was running an old code version. I ...

Turns out I tried to invent a brand new addressing mode! I needed to 'peek' at the next byte coming up to calculate the mid-point between the hi-nibble of current byte and low nibble of next byte. Somehow I thought I could do a "LDA mySelfModPtr" from the 'peeking' code as well. Doh! I was working ...

Thanks, That is a clever way to do it.

I have both versions working and both sound awful. The version that changes the NMI address take up more memory but is a bit faster. Your version is smaller, takes a little longer but is more clear as to what is happening I think.

I suspect it is an issue ...

Back in April I had asked a question about methods of toggling a single bit as a flag. The suggestions were very helpful and some clever alternatives were proposed. This was for a C64 'DIGI' player I had starting working on in January. I was finally able to incorporate the suggestions this past ...

I wanted to thank everyone for their help. I got a bit distracted form this project for a few weeks but implemented the changes suggest by Chromatix and it works quite well. The number of cycles though each path is also very close. I started producing a video about playing DIGIs on the C64 which I ...

Thank you Chromatix. I did not get a chance to get back to this today. I set out to test how the C64 diagnostic harness worked on the C128 with a PCB a friend designed for the KB dongle and the C128 quit right in front of me. No clock coming out of the 8701 clock generation chip, but the 8701 itself ...

Here is the NMI for the DIGI player. One thing that just occurred to me is that I could make sure that the samples always end on a page boundary. That way I only need to compare the high byte of the sample ending address. That would save 9-10 cycles.

It might also be interesting to look at using a ...

The same code, with different initialisation values, can be used to generate a set (or cleared) bit every 2 cycles, every 4 cycles, or every 8 cycles - indeed, in any repeating pattern of length 8. The execution time is 12 cycles for every set bit, and 8 cycles for every cleared bit. It has the ...